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A99.9 F7622Uf VSDA
Assessing Urban Forest
Foestse^ice Effects Bncl Values
Resource Bulletin NE-166
Minneapolis' Urban Forest
An analysis of trees in Minneapolis, MN, reveals that the city has about 979,000 trees with
canopies that cover 26.4 percent of the area. The most common tree species are green ash,
American elm, and boxelder. The urban forest currently stores about 250,000 tons of carbon
valued at $4.6 million. In addition, these trees remove about 8,900 tons of carbon per year
($164,000 per year) and trees and shrubs combined remove about 384 tons of air pollution
per year ($1 .9 million per year). The structural, or compensatory, value is estimated at $756
million. Information on the structure and functions of the urban forest can be used to improve
and augment support for urban forest management programs and to integrate urban forests
within plans to improve environmental quality in the Minneapolis area.
DAVID J. NOWAK is a research forester and project leader, ROBERT E. HOEHN III, is a
biological sciences technician, DANIEL E. CRANE is an information technology specialist,
JACK C. STEVENS is a forester, and JEFFREY T WALTON is a research forester with
the Forest Service's Northeastern Research Station at Syracuse, NY. JERRY BOND is a
consulting urban forester and GREG INA is a manager of geographic information systems/
information technology with the Davey Resource Group at Kent, OH.
Published by: For additional copies:
USDA FOREST SERVICE USDA Forest Service
1 1 CAMPUS BLVD SUITE 200 Publications Distribution
NEWTOWN SQUARE PA 19073-3294 359 Main Road
Delaware, OH 43015-8640
May 2006 Fax: (740)368-01 52
Visit our homepage at: http://www.fs.fed.us/ne
benefits to society,
yet relatively little
is known about this
In 2004, the UFORE
model was used to
survey and analyze
benefits of the
still remain to be
Trees in cities can contribute significantly to human health and environmental quality.
Unfortunately, little is known about the urban forest resource and what it contributes
to the local and regional society and economy. To better understand the urban forest
resource and its numerous values, the USDA Forest Service, Northeastern Research
Station, developed the Urban Forest Effects (UFORE) model. Results from this model
are used to advance the understanding of the urban forest resource, improve urban
forest policies, planning and management, provide data for potential inclusion of trees
within environmental regulations, and determine how trees affect the environment and
consequently enhance human health and environmental quality in urban areas.
Forest structure is a measure of various physical attributes of the vegetation, such as
tree species composition, number of trees, tree density, tree health, leaf area, biomass,
and species diversity. Forest functions, which are determined by forest structure,
include a wide range of environmental and ecosystem services such as air pollution
removal and cooler air temperatures. Forest values are an estimate of the economic
worth of the various forest functions.
To help determine the vegetation structure, functions, and values of the urban forest
in Minneapolis, a vegetation assessment was conducted during the summer of 2004.
For this assessment, one-tenth acre field plots were sampled and analyzed using the
UFORE model. This report summarizes results and values of
• Forest structure • Carbon storage
• Risk of insect pests and diseases • Annual carbon removal (sequestration)
• Air pollution removal • Changes in building energy use
More detailed information can be found at: www.fs.fed.us/ne/syracuse/Data/data.htm.
Minneapolis Urban Forest Summary
Number of trees
Most common species
green ash, American elm.
Percentage of trees
< 6-inches diameter
384 tons/year ($1.9 million/year)
250,000 tons ($4.6 million)
8,900 tons/year ($l64,000/year)
BuUding energy reduction
Avoided carbon emissions
Ton - short ton (U.S.) (2,000 lbs)
Urban Forest Effects Model
and Field Measurements
Though urban forests have many functions and values, currently only a few of these
attributes can be assessed. To help assess the city's urban forest, data from 110 field
plots located throughout the city were analyzed using the Forest Service's Urban Forest
Effects (UFORE) model.'
Benefits ascribed to
urban trees include:
• Air pollution
• Air temperature
• Reduced building
• Improved water
• Reduced noise
• Improved human
UFORE is designed to use standardized field data from randomly located plots and
local hourly air pollution and meteorological data to quantify urban forest structure
and its numerous effects, including:
• Urban forest structure (e.g., species composition, tree density, tree health, leaf
area, leaf and tree biomass, species diversity, etc.).
• Amount of pollution removed hourly by the urban forest and its associated
percent air quality improvement throughout a year. Pollution removal is
calculated for ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide and
particulate matter (<10 microns).
• Total carbon stored and net carbon annually sequestered by the urban forest.
• Effects of trees on energy use in buildings and consequent effects on carbon
dioxide emissions from power plants.
• Compensatory value of the forest, as well as the value for air pollution removal
and carbon storage and sequestration.
• Potential impact of infestations by Asian longhorned beetles, emerald ash
borers, gypsy moth, and Dutch elm disease.
For more information go to http://www.ufore.org
In the field, one-tenth acre plots were randomly located within a grid pattern at a
density of approximately one plot every 340 acres. In Minneapolis, service districts
were used to divide the analysis into smaller
zones. The plots were divided among the
following service districts: River District
(49 plots). Lakes District (31 plots), and
Minnehaha District (30 plots).
Field Survey Data
• Land use type
• Percent tree cover
• Percent shrub
• Percent plantable
• Percent ground
• Shrub species /
• Stem diameter
• Total height
• Height to crown
• Crown width
• Percent foliage
• Percent dieback
• Crown light
• Distance and
Field data were collected by Davey Resource Group during the leaf-on season to
properly assess tree canopies. Within each plot, data included land use, ground and
tree cover, shrub characteristics, and individual tree attributes of species, stem diameter
at breast height (d.b.h.; measured at 4.5 ft), tree height, height to base of live crown,
crown width, percentage crown canopy missing and dieback, and distance and
direction to residential buildings. -
To calculate current carbon storage, biomass for each tree was calculated using
equations from the literature and measured tree data. Open-grown, maintained trees
tend to have less biomass than predicted by forest-derived biomass equations.-^ To
adjust for this difference, biomass results for open-grown urban trees are multiplied by
0.8.^ No adjustment is made for trees found in natural stand conditions. Tree dry-
weight biomass was converted to stored carbon by multiplying by 0.5.
To estimate the gross amount of carbon sequestered annually, average diameter growth
from the appropriate genera and diameter class and tree condition was added to the
existing tree diameter (year x) to estimate tree diameter and carbon storage in year x+ 1 .
Air pollution removal estimates are derived from calculated hourly tree-canopy
resistances for ozone, and sulfur and nitrogen dioxides based on a hybrid of big-leaf
and multi-layer canopy deposition models.^'^ As the removal of carbon monoxide
and particulate matter by vegetation is not directly
related to transpiration, removal rates (deposition
velocities) for these pollutants were based on
average measured values from the literature^'^ that
were adjusted depending on leaf phenology and
leaf area. Particulate removal incorporated a 50
percent resuspension rate of particles back to the
Seasonal effects of trees on energy use in residential
building was calculated based on procedures
described the literature^ using distance and direction
of trees from residential structures, tree height and
tree condition data.
Compensatory values were based on valuation
procedures of the Council of Tree and Landscape
Appraisers, which uses tree species, diameter, conditii
To learn more about UFORE methods" visit:
http://www.fs.fed.us/ne/syracuse/Data/data.htm or www.ufore.org
Tree Characteristics of the Urban Forest
There are an
trees in IVIinneapolis
with canopies that
cover 26.4 percent
of the city.
The 10 most
account for 75
percent of the total
number of trees.
The urban forest of Minneapolis has an estimated 979,000 trees and a tree cover of
26.4 percent. Trees with diameters less than 6 inches account for 47.3 percent of the
population. The three most common species are green ash (21.6 percent), American
elm (17.1 percent), and boxelder (9.1 percent). The 10 most common species account
for 75 percent of all trees; their relative abundance is illustrated below.
Tree density is
highest in the Lakes
District, lowest in
the River District.
The highest density of trees occurs in the Lakes District (31.6 trees/acre), followed by
the Minnehaha District (29.0 trees/acre) and the River District (19.8 trees/acre). The
overall tree density in Minneapolis is 26.2 trees/acre, which is within the range of other
city tree densities (Appendix I), of 14.4 to 119.2 trees/acre.
quarters of the
tree species in
native to Minnesota.
Urban forests are
a mix of native
tree species that
existed prior to the
the city and exotic
species that were
residents or other
Urban forests are a mix of native trees species that existed prior to the development
of the city and exotic species that were introduced by residents or other means.
Thus, urban forests often have a tree diversity that is higher than surrounding native
landscapes. An increased tree diversity can minimize the overall impact or destruction
by a species-specific insect or disease, but the increase in the number of exotic plants
can also pose a risk to native plants if some of the exotics species are invasive plants
that can potentially out-compete and displace native species. In Minneapolis, about
80 percent of the trees are species native to North America, while 74 percent are native
to the state. Species exotic to Minnesota make up 26 percent of the population. Most
exotic tree species have an origin from Eurasia (9.2 percent of the species).
*North America + refers to tree species that are native to North America and one other continent.
Urban Forest Cover and Leaf Area
Trees cover about 26.4 percent of Minneapolis and shrubs cover 6 percent of the city.
Dominant ground cover types include herbaceous (e.g., grass, gardens) (34.0 percent),
impervious surfaces (excluding buildings) (e.g., driveways, sidewalks, parking lots)
(33.6 percent), and buildings (18.0 percent).
Healthy leaf area
to tree benefits
provided to the
Green ash has the
to the IVIinneapolis
urban forest based
on relative leaf
area and relative
'^Percent leaf area
^Importance value (%Pop + %LA)
I bare soil
I impervious surfaces (excluding buildings)
Many tree benefits are linked directly to the amount of healthy leaf surface area of
the plant. In Minneapolis, trees that dominate in terms of leaf area are green ash,
American elm, and silver maple.
Tree species with relatively large individuals contributing leaf area to the population
(species with percentage of canopy much greater than percentage of population) are
silver maple, bur oak, and sugar maple. Smaller trees in the population are American
basswood, northern white cedar, and boxelder (species with percentage of canopy
much less than percentage of population). A species must also constitute at least 1
percent of the total population to be considered as relatively large or small trees in the
Tree importance values (IV) are calculated using a formula that takes into account the
relative leaf area and relative composition. The most important species in the urban
forest, according to calculated IVs, are green ash, 7\merican elm, and silver maple.
% of total leaf area
I % of all trees
The urban forest
removes about 384
tons of pollutants
each year, with a
value to society of
to improve air
quality are given in
Air Pollution Removal by Urban Trees
Poor air quality is a common problem in many urban areas. It can lead to human
health problems, damage to landscape materials and ecosystem processes, and reduced
visibility. The urban forest can help improve air quality by reducing air temperature,
directly removing pollutants from the air, and reducing energy consumption in
buildings, which consequently reduce air pollutant emissions from power plants.
Trees also emit volatile organic compounds that can contribute to ozone formation.
However, integrative studies have revealed that an increase in tree cover leads to
reduced ozone formation.'-
Pollution removal by trees and shrubs in Minneapolis was estimated using field data
and hourly pollution and weather data for 2000. Pollution removal was greatest for
particulate matter less than ten microns (PM^^j), followed by ozone (O^), nitrogen
dioxide (NOJ, sulfur dioxide (SOJ, and carbon monoxide (CO). It is estimated that
trees and shrubs remove 384 tons of air pollution (CO, NO,, O^, PM^^, SO J per
year with an associated value of $1.9 million (based on estimated national median
externality costs associated with pollutants'-'). Trees remove about four times more air
pollution than shrubs in Minneapolis.
The average percentage of air pollution removal during the daytime, in-leaf season was
estimated to be:
Peak 1-hour air quality improvements during the in-leaf season for heavily-treed areas
(100% tree cover) was estimated to be:
■ Pollution Removed
— Value (U.S. Dollars)
held In tree tissue
(roots, stems, and
of carbon removed
trees. Net carbon
can be negative If
emission of carbon
Is greater than
by healthy trees.
Carbon Storage and Sequestration
Climate change is an issue of global concern. Urban trees can help mitigate climate
change by sequestering atmospheric carbon (from carbon dioxide) in tissue and by
reducing energy use in buildings, consequently reducing carbon dioxide emissions
from fossil-fuel based power plants.'^
Trees reduce the amount of carbon in the atmosphere by sequestering carbon in new
tissue growth every year. The amount of carbon annually sequestered is increased
with healthier trees and larger diameter trees. Minneapolis' trees gross sequestration is
about 8,900 tons of carbon per year with an associated value of $164,000. Net carbon
sequestration in the Minneapolis urban forest is about 4,200 tons.
1 ,800 n
- 17,000 ■§
<? <? cj
<9 & >
C) (7) ^7*
Carbon storage by trees is another way trees can influence global climate change. As
trees grow, they store more carbon by holding it in their accumulated tissue. As trees
die and decay, they release much of the stored carbon back into the atmosphere. Thus,
carbon storage is an indication of the amount of carbon that can be lost if trees are
allowed to die and decompose. Trees in Minneapolis are estimated to store 250,000
tons of carbon ($4.6 million). Of all the species sampled, American elm stores and
sequesters the most carbon (about 18.6 percent of the total carbon stored and 19.2
percent of all sequestered carbon).
■i Carbon Storage
-*- Carbon Sequestration
Trees affect energy
and blocking winter |
between buildings |
and trees save an j
estimated $221,000 \
in heating and ;
Lower energy use ini
reduced carbon i
power plants by 900
Trees Affect Energy Use in Buildings
Trees affect energy consumption by shading buildings, providing evaporative cooling,
and blocking vi^inter winds. Trees tend to reduce building energy consumption in the
summer months and can either increase or decrease building energy use in the winter
months, depending on the location of trees around the building. Estimates of tree
effects on energy use are based on field measurements of tree distance and direction to
space-conditioned residential buildings.^
Based on 2002 energy costs, trees in Minneapolis are estimated to reduce energy costs
from residential buildings by $221,000 annually. Trees also provide an additional
$15,900 in value by reducing the amount of carbon released by fossil-fuel based power
plants (a reduction of 900 tons of carbon emissions).
Annual energy savings due to trees near residential buildings. Note:
negative numbers indicate an increase in energy use or carbon emissions.
Carbon avoided (t)
''Million British Thermal Units
Annual savings'^ (U.S. $) in residential energy expenditure during
heating and cooling seasons. Note: negative numbers indicate a cost
due to increased energy use or carbon emissions.
^Million British Thermal Units
■^Based on state-wide energy cost
structural and Functional Values
Urban forests have a structural value based on the tree itself (e.g., the cost of having
to replace the tree with a similar tree). The structural value'° of urban forest in
Minneapolis is about $756 million. The structural value of an urban forest tends to
increase with a rise in the number and size of healthy trees.
Urban forests have
a structural value
based on the tree
Urban forests also
values based on the
functions the tree
provide the greatest
Urban forests also have functional values (either positive or negative) based on the
functions the tree performs. Annual functional values also tend to increase with
increased number and size of healthy trees, and are usually on the order of several
million dollars per year. There are many other functional values of the urban forest,
though they are not quantified here (e.g., reduction in air temperatures and ultra-
violet radiation, improvements in water quality). Through proper management, urban
forest values can be increased. However, the values and benefits also can decrease as the
amount of healthy tree cover declines.
• Structural value: $756 million
• Carbon storage: $4.6 million
Annual functional values:
• Carbon sequestration: $164,000
• Pollution removal: $1.9 million
• Lower energy costs and carbon emission reductions: $237,000
More detailed information on the urban forest in Minneapolis can be found at www.
fs.fed.us/ne/syracuse/Data/data.htm. Additionally, information on other urban
forest values can be found in Appendix I and information comparing tree benefits to
estimates of average carbons emissions in the city, average automobile emissions, and
average household emissions can be found in Appendix III.
Michigan State University
USDA Forest Service Archives
Potential Insect and Disease Impacts
Various insects and diseases can infest urban forests, potentially killing trees and
reducing the health, value and sustainability of the urban forest. As various pests have
differing tree hosts, the potential damage or risk of each pest will differ. Four exotic
pests w^ere analyzed for their potential impact: Asian longhorned beetle, gypsy moth,
emerald ash borer, and Dutch elm disease.
The Asian longhorned beetle (ALB)'' is an insect that bores into and kills a wide range
of hardwood species. ALB represents a potential loss to the Minneapolis urban forest
of $487 million in structural value (68.1 percent of the tree population).
The gypsy moth (GM)"^ is a defoliator that feeds on many species causing widespread
defoliation and tree death if outbreak conditions last several years. This pest could
potentially result in a loss of $80 million in structural value (10.1 percent of the tree
Emerald ash borer (EAB)''' has killed thousands of ash trees in Michigan, Ohio, and
Indiana. EAB has the potential to affect 22.0 percent of the population ($148 million
in structural value).
American elm, one of the most important street trees in the 20th century, has been
devastated by the Dutch elm disease (DED). Since first reported in the 1930s, it
has killed more than 50 percent of the native elm population in the United States.'^
Although some elm species have shown varying degrees of resistance, Minneapolis
possibly could lose 17.1 percent of its trees to this disease ($l4l million in structural
Appendix I. Comparison of Urban Forests
A commonly asked question is, "How does this city compare to other cities?" Although comparison among
cities should be made with caution as there are many attributes of a city that affect urban forest structure and
functions, summary data are provided from other cities analyzed using the UFORE model.
I. City totals, trees only
l^ol Ti 1 f"!r\n A/o 1 n^^
1 L/11U.LHJI1 VdlU-C
Number of trees
/ / c c\r\c\
1 / r\r\
1 /" 1 1 AAA
O / 1 C f\f\f\
1 "XAA (\C\C\
/if A f\C\
o 2 T 1 AAA
r 1 AC AAA
Npw York MY^"
1 ^SO 000
0,U/ i ,UUv/
1 COl 000
San Francisco, CA^
Jersey City, NJ^
II. Per acre values of tree effects
^e Carbon sequestration Poll
No. of trees
New York, NY*'
San Francisco, CA*
Jersey City, NJ*^
Data collection group
^ City personnel
' Casey Trees Endowment Fund
^ New Jersey Department of Environmental Protect!
University of Toronto
8 Davey Resource Group
^ U.S. Forest Service
West Virginia University
Appendix II. General Recommendations for Air Quality Improvement
Urban vegetation can directly and indirectly affect local and regional air quality by altering the urban atmospheric
environment. Four main ways that urban trees affect air quality are:
Temperature reduction and other microclimatic effects
Removal of air pollutants
Emission of volatile organic compounds (VOC) and tree maintenance emissions
Energy conservation in buildings and consequent power plant emissions
The cumulative and interactive effects of trees on climate, pollution removal, and VOC and power plant emissions
determine the overall impact of trees on air pollution. Cumulative studies involving urban tree impacts on ozone
have revealed that increased urban canopy cover, particularly with low VOC emitting species, leads to reduced ozone
concentrations in cities. Local urban forest management decisions also can help improve air quality.
Urban forest management strategies to help improve
air quality include:
Increase the number of healthy trees
Sustain existing tree cover
Maximize use of low VOC-emitting trees
Sustain large, healthy trees
Use long-lived trees
Use low maintenance trees
Reduce fossil fuel use in maintaining vegetation
Plant trees in energy conserving locations
Plant trees to shade parked cars
Supply ample water to vegetation
Plant trees in polluted or heavily populated areas
Avoid pollutant-sensitive species
Utilize evergreen trees for particulate matter
Increase pollution removal
Maintain pollution removal levels
Reduces ozone and carbon monoxide formation
Large trees have greatest per-tree effects
Reduce long-term pollutant emissions from planting and removal
Reduce pollutants emissions from maintenance activities
Reduce pollutant emissions
Reduce pollutant emissions from power plants
Reduce vehicular VOC emissions
Enhance pollution removal and temperature reduction
Maximizes tree air quality benefits
Improve tree health
Year-round removal of particles
Appendix III. Relative Tree Effects
The urban forest in Minneapohs provides benefits that include carbon storage and sequestration, and air pollutant
removal. To estimate a relative value of these benefits, tree benefits were compared to estimates of average carbon
emissions in city^^, average passenger automobile emissions-*^, and average household emissions.^'
General tree information:
Average tree diameter (d.b.h.) = 10.3 in.
Median tree diameter (d.b.h.) = 6.7 in.
Average number of trees per person = 2.6
Number of trees sampled = 278
Number of species sampled = 41
Average tree effects by tree diameter:
" miles = numbi
er of automobi
le miles driven that p
reduces emissions equivaJ
The Minneapolis urban forest provides:
Carbon storage equivalent to:
Amount of carbon (C) emitted in city in 40 days or
Annual C emissions from 150,000 automobiles or
Annual C emissions from 75,500 single family houses
Carbon monoxide removal equivalent to:
Annual carbon monoxide emissions from 31 automobiles or
Annual carbon monoxide emissions from 100 single family
Nitrogen dioxide removal equivalent to:
Annual nitrogen dioxide emissions from 2,900 automobiles or
Annual nitrogen dioxide emissions from 1,900 single family
Sulfur dioxide removal equivalent to:
Annual sulfur dioxide emissions from 19,900 automobiles or
Annual sulfur dioxide emissions from 300 single family houses
Particulate matter less than 10 micron (PM ^ ^) removal
Annual PMIO emissions from 315,600 automobiles or
Annual PMIO emissions from 30,500 single family houses
Annual C sequestration equivalent to:
Amount of C emitted in cit}' in 1 .4 days or
Annual C emissions from 5,300 automobiles or
Annual C emissions from 2,700 single family homes
Appendix IV. List of Species Sampled in Minneapolis
Potential pest ^
% Leaf Area
1 . 1
European white birch
eastern white pine
jy 1 V Ll lo
Appendix IV continued.
To Lear Area
<jM hAJb JJhJJ
purpieiear sand cherry
northern red oak
northern white cedar
""IV = importance value (% population + % leaf area)
''ALB = Asian longhorned beetle; GM = g}'psy moth; EAB = emerald ash borer; DED = Dutch elm disease
1 Nowak, D.J.; Crane, D.E. 2000. The Urban Forest
Effects (UFORE) Model: quantiiying urban
forest structure and functions. In: Hansen, M.;
Burk, T., eds. Integrated tools for natural resources
inventories in the 21st century. Proceedings of
lUFRO conference. Gen. Tech. Rep. NC-212. St.
Paul, MN: U.S. Department of Agriculture, Forest
Service, North Central Research Station: 714-720.
2 Nowak, D.J.; Crane, D.E.; Stevens, J.C.; Hoehn, R.E.
2005. The urban forest effects (UFORE) modeh
field data collection manual. VI b. [Nev^aown
Square, PA]: U.S. Department of Agriculture,
Forest Service, Northeastern Research Station. 34 p.
http : //www. fs .fed. us/ ne/ syracuse/Tools/ downloads/
3 Nowak, D.J. 1994. Atmospheric carbon dioxide
reduction by Chicago's urban forest. In:
McPherson, E.G.; Nowak, D.J.; Rowntree, R.A.,
eds. Chicago's urban forest ecosystem: results of
the Chicago Urban Forest Climate Project. Gen.
Tech. Rep. NE-186. Radnor, PA: U.S. Department
of Agriculture, Forest Service, Northeastern Forest
Experiment Station: 83-94.
4 Baldocchi, D. 1988. A multi-layer model for
estimating sulfur dioxide deposition to a
deciduous oak forest canopy. Atmospheric
Environment. 22: 869-884.
5 Baldocchi, D.D.; Hicks, B.B.; Camara, P 1987. A
canopy stomatal resistance model for gaseous
deposition to vegetated surfaces. Atmospheric
Environment. 21: 91-101.
6 Bidwell, R.G.S.; Fraser, D.E. 1972. Carbon
monoxide uptake and metabolism by leaves.
Canadian Journal of Botany. 50: 1435-1439.
7 Lovett, G.M. 1994. Atmospheric deposition of
nutrients and pollutants in North America: an
ecological perspective. Ecological Applications. 4:
8 Zinke, P.J. 1967. Forest interception studies in the
United States. In: Sopper, W.E.; Lull, H.W., eds.
Forest hydrology. Oxford, UK: Pergamon Press:
9 McPherson, E.G.; Simpson, J. R. 1999. Carbon
dioxide reduction through urban forestry:
guidelines for professional and volunteer tree
planters. Gen. Tech. Rep. PSW-171. Albany, CA:
U.S. Department of Agriculture, Forest Service,
Pacific Southwest Research Station. 237 p. Can
be accessed through http://www.fs.fed.us/psw/
10 Nowak, D.J.; Crane, D.E.; Dwyer, J.E 2002.
Compensatory value of urban trees in the United
States. Journal of Arboriculture. 28(4): 194-199.
1 1 Nowak, D.J.; Crane, D.E.; Stevens, J.C.; Ibarra, M.
2002. Brooklyn's urban forest. Gen. Tech. Rep.
NE-290. Newtown Square, PA: U.S. Department of
Agriculture, Forest Service, Northeastern Research
Station. 107 p.
12 Nowak D.J.; Dwyer, J.E 2000. Understanding
the benefits and costs of urban forest ecosystems.
In: Kuser, John E., ed. Handbook of urban and
community forestry in the northeast. New York:
Kluwer Academics/Plenum: 1 1-22.
13 Murray, F.J.; Marsh L.; Bradford, PA. 1994. New
York state energy plan, vol. II: issue reports.
Albany, NY: New York State Energy Office.
14 Abdollahi, K.K.; Ning, Z.H.; Appeaning, A., eds.
2000. Global climate change and the urban
forest. Baton Rouge, LA: GCRCC and Franklin
Press. 77 p.
1 5 Northeastern Area State and Private Forestry. 2005.
Asian Longhomed Beetle. Newtown Square, PA:
U.S. Department of Agriculture, Northeastern Area
State and Private Forestry, http://www.na.fs.fed.
16 Northeastern Area State and Private Forestry.
2005. Gypsy moth digest. Newtown Square, PA:
U.S. Department of Agriculture, Forest Service,
Northeastern Area State and Private Forestry.
17 Northeastern Area State and Private Forestry. 2005.
Forest health protection emerald ash borer
home. Newtown Square, PA: U.S. Department of
Agriculture, Forest Service, Northeastern Area
State and Private Forestry, http://www.na.fs.fed.
18 Stack, R.W.; McBride, D.K.; Lamey, H.A. 1996.
Dutch elm disease. PP-324 (revised). Fargo,
ND: North Dakota State Universit}', Cooperative
Extension Service, http://www.ext.nodak.edu/
extpubs/ plantsci/ trees/ pp324w.htm
Explanation of Calculations of Appendix III
1 9 Total city carbon emissions were based on 2003
U.S. per capita carbon emissions, calculated as
total U.S. carbon emissions (Energy Information
Administration, 2003, Emissions of Greenhouse
Gases in the United States 2003. http://www.eia.
doe.gov/oiaf/l605/l605aold.html) divided by
2003 total U.S. population (www.census.gov). Per
capita emissions were multiplied by Minneapolis
population to estimate total city carbon emissions.
20 Average passenger automobile emissions per
mile were based on dividing total 2002 pollutant
emissions from light-duty gas vehicles (National
Emission Trends http://www.epa.gov/ttn/chief/
trends/index.html) by total miles driven in 2002 by
passenger cars (National Transportation Statistics
Average annual passenger automobile emissions
per vehicle were based on dividing total 2002
pollutant emissions from light-duty gas vehicles
by total number of passenger cars in 2002
(National Transportation Statistics http://www.
Carbon dioxide emissions from automobiles
assumed 6 pounds of carbon per gallon of gasoline
with energy costs of refinement and transportation
included (Graham, R.L.; Wright, L.L.; Turhollow,
A.F. 1992. The potential for short-rotation woody
crops to reduce U.S. CO^ emissions. Climatic
21 Average household emissions based on average
electricity kWh usage, natural gas Btu usage, fuel oil
Btu usage, kerosene Btu usage, LPG Btu usage, and
wood Btu usage per household from:
Energy Information Administration. Total Energy
Consumption in U.S. Households by Type of
Housing Unit, 2001 www.eia.doe.gov/emeu/recs/
recs200 1 / detailcetbls.html.
CO^, SO^, and NOx power plant emission per
U.S. Environmental Protection Agency. U.S.
power plant emissions total by year www.epa.gov/
CO emission per kWh assumes one-third of 1
percent of C emissions is CO based on:
Energy Information Administration. 1994.
Energy use and carbon emissions: non-OECD
countries. DOE/EIA-0579(94). Washington,
DC: Department of Energy, Energy Information
PMjQ emission per kWh from:
Layton, M. 2004. 2005 Electricity environmental
performance report: electricity generation and air
emissions. Sacramento, CA: California Energy
documents/2004- 11-1 5_workshop/2004- 11-1 5_03-
CO,, NOx, SO^, PM,Q, and CO emission per Btu
for natural gas, propane and butane (average used
to represent LPG), Fuel #4 and #6 (average used to
represent fuel oil and kerosene) from:
Abraxas energy consulting. http://www.
CO-, and fine particle emissions per Btu of wood
Houck, J.E.; Tiegs, PE.; McCrillis, R.C.; Keithley,
C; Crouch, J. 1998. Air emissions from residential
heating: the wood heating option put into
environmental perspective. In: Proceedings of U.S.
EPA and Air and Waste Management Association
conference: living in a global environment, V. 1:
CO, NOx and SOx emission per Btu of wood based
on total emissions from wood burning (tonnes) from:
Residential Wood Burning Emissions in British
Columbia. 2005. http://www.env.gov.bc.ca/air/
Emissions per dry tonne of wood converted to
emissions per Btu based on average dry weight per
cord of wood and average Btu per cord from:
Kuhns, M.; Schmidt, T. 1988. Heating with wood:
species characteristics and volumes I. NebGuide
G-88-881-A. Lincoln, NE: University of Nebraska,
Institute of Agriculture and Natural Resources,
Nowak, David J.; Hoehn, Robert E. Ill, Crane, Daniel E.; Stevens, Jack C; Walton,
Jeffrey T. 2006. Assessing urban forest effects and values, Minneapolis'
urban forest. Resour. Bull. NE-166. Newtown Square, PA: U.S. Department of
Agriculture, Forest Service, Northeastern Research Station. 20 p.
An analysis of trees in Minneapolis, MN, reveals that the city has about 979,000
trees with canopies that cover 26.4 percent of the area. The most common tree
species are green ash, American elm, and boxelder The urban forest currently
stores about 250,000 tons of carbon valued at $4.6 million. In addition, these
trees remove about 8,900 tons of carbon per year ($164,000 per year) and trees
and shrubs combined remove about 384 tons of air pollution per year ($1 .9
million per year). The structural, or compensatory, value is estimated at $756
million. Information on the structure and functions of the urban forest can be used
to improve and augment support for urban forest management programs and
to integrate urban forests within plans to improve environmental quality in the
Keywords: urban forestry; ecosystem services; air pollution removal; carbon
sequestration; tree value
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Headquarters of the Northeastern Research Station is in Newtown Square,
Pennsylvania. Field laboratories are maintained at:
Amherst, Massachusetts, in cooperation with the University of Massachusetts
Burlington, Vermont, in cooperation with the University of Vermont
Durham, New Hampshire, In cooperation with the University of New Hampshire
Hamden, Connecticut, in cooperation with Yale University
Morgantown, West Virginia, in cooperation with West Virginia University
Parsons, West Virginia
Princeton, West Virginia
Syracuse, New York, in cooperation with the State University of New York,
College of Environmental Sciences and Forestry at Syracuse University
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